MRAM is a memory which holds data by storing information in the spin which an electron has, and the circuit is formed so that the random access is possible. There is a type which uses GMR (Giant Magneto Resistance), TMR, and CMR (Colossal Magneto Resistance) as a basic physical phenomenon.
TMR is a type using the resistance change phenomenon observed in the structure which sandwiches an insulating layer with the magnetic film of two layers. In the state of the spin of the up-and-down magnetic layer which sandwiches an insulating layer, the current (namely, resistance of TMR) which flows through an upper magnetic layer—an insulating layer—a bottom magnetic layer changes. Resistance becomes small when two spin states of an up-and-down magnetic layer are parallel, and if it is antiparallel, resistance becomes large. This change in resistance can perform information storage. There is Patent Reference 1 as literature which disclosed the magnetic memory equipment which has such a TMR element, and its manufacturing method. There is also structure called a MTJ (Magnetro-Tunneling Junction) element as an element of the same structure as TMR. Hereafter, a “TMR element” includes an MTJ element not only a TMR element but widely in a present application specification. [Patent Reference 1] Japanese Unexamined Patent Publication No. 2003-243630